The holographic principle, which purports that a quantum theory of gravity can be captured by an ordinary non-gravitational theory in fewer dimensions, offers a profound perspective on the nature of quantum gravity.
At present, the AdS/CFT correspondence [1]} remains our best-established and most thoroughly investigated example of this paradigm. In asymptotically flat spacetimes, the scattering problem nevertheless suggests a way in which the holographic principle might naturally extend to this context. In particular, since the observables associated with scattering in asymptotically flat space depend only on data characterizing the states at asymptotically early and late times, they reside by construction in the fewer dimensions of the past and future boundaries of spacetime.
